This invention relates generally to inertial navigation systems of the type including a primary gyro/accelerometer triad and particularly to an arrangement wherein system performance is validated by comparing data measured by a fourth gyro/accelerometer to an analytical equivalent established from measurements made by the primary triad.
Current land vehicle weapon scenarios involve "shoot and scoot" procedures. That is to say, radar tracks the ballistic trajectory of a first enemy round, determines the firing site of the round and directs opposing fire before the first enemy round has landed. A high degree of mobility is required, i.e. fire opposing rounds for effect and depart firing sites quickly.
Stable reference platform navigation systems gyrocompass in a relatively secure "hide zone" while the land vehicle is stationary. When a fire mission is initiated the vehicle may travel tens of kilometers over a few hours. The objective, as aforenoted, is to fire a round quickly and to vacate the fire site.
The massive firepower of modern land vehicle weapons systems poses a significant problem, i.e. the adverse consequences of misdirected fire. The need to validate firing accuracy to better than five mils of attitude error leads to the conclusion that a second system which enables comparison of results against an error criteria be implemented. Indeed, a stable reference platform mechanization does not allow for an independent measurement short of using a second system. It is of special significance to be able to validate attitude while the vehicle is moving.